It is a dialogue (B).
Although the author presents the speech of only one of the interlocutors, the English teacher, it is perceptible that there is a passive interlocutor, the student. The dialogue gives the reader the perception of the present moment in the scene. Thus, new information can be inserted, in a more intense emotional level, reaching greater depth in the hostory. This is what happens in this passage. The teacher talks in an appealing tone with the student. Another way of analyzing the dialogue is through punctuation. The words spoken by the character are accompanied by quotation marks or dashes.